Air
operated liquid level sensor is intrinsically safe because it uses no
electronics. Therefore it can be operated in hazardous areas. The
sensor probe sits in the tank and send an air signal to a valve when
the liquid level is either too low or too high.

For example if you have a daily use ink or adhesive container and want
to fill it from a 55 gallon drum or Tote tank you could setup the
sensor to operate a double diaphragm or peristaltic pump when the daily
tank runs low. The remote pump will fill the daily tank without the use
of any expensive or large explosionproof electronics